An aide to Republican presidential nominee Donald Trump says she made a mistake in writing his wife Melania's tribute to him this week by including identical phrases from a speech Michelle Obama gave supporting her husband Barack Obama's 2008 run for the U.S. presidency.

For two days, the Trump campaign belittled complaints that Melania Trump had plagiarized portions of Michelle Obama's address in her Monday night speech to the Republican National Convention about her husband of 11 years.

But on Wednesday, Trump aide Meredith McIver, a one-time ballet dancer who helped write some of his books, said she offered to resign over the controversy that has consumed some of the news coverage of this week's convention in Cleveland, Ohio. But she said the presidential contender rejected her offer.

McIver said that as she set out to write Melania Trump's speech, the would-be first lady read her some passages from Michelle Obama's speech to her over the phone. McIver said she took notes and later included some of the phrasing in the final draft.

But McIver said she did not check Michelle Obama's 2008 speech at the Democratic National Convention ahead of the first of her husband's two successful presidential campaigns.

"That was my mistake," McIver said, "and I feel terrible for the chaos I have caused Melania and the Trumps, as well as to Mrs. Obama. No harm was meant."

McIver said that "Mr. Trump told me that people make innocent mistakes and that we learn and grow from these experiences."